Suspension systems of the type described above are used, for example but by no means exclusively, in trucks, agricultural vehicles or heavy-load vehicles, in order to decouple the driver's cabin from the vehicle's chassis as much as possible, in each case with regard to vibrations and movements.
Since in heavy-load vehicles the spring and damper characteristics of the spring/damper units of the chassis have to be chosen unavoidably ‘hard’ on account of the considerably large vehicle weight and because of the large unsprung masses in the chassis, bumpiness of the road or even vibrations from the axles and drive-train are still often transmitted to a considerable extent, via the axle springing, to the chassis and from there also to the driver's cabin.
In the context of ergonomics and work protection for the driver, in order to minimize transmitting such shocks and vibrations to the driver's cabin and thus to the place where the driver works, driver's cabin suspensions have been developed by which the driver's accommodation or cabin is supported on the vehicle chassis by means of a suspension system of its own. Thanks to the much lower mass of the driver's cabin compared with the vehicle, such suspension systems for the driver's cabin can be designed with ‘softer’ spring characteristics than the axle suspension, and for that reason bumpiness of the road or vibrations coming from the drive-train or axles of the vehicle can be much more effectively isolated from where the driver works, thanks to such comparatively softer cabin suspension systems.
With elastic suspension systems of this type, in order for example to restrict lateral movements or even rolling of the driver's cabin—as when driving on an incline or round a curve, but also for example in the case of road bumps on one side only—suspension systems have been developed in which a spring/damper arrangement and a Watt linkage mechanism is disposed between the driver's cabin and the chassis. Depending on the design, the Watt linkage mechanism ensures that lateral movements of the vehicle's cabin relative to the chassis are suppressed, or that the sprung movements of the cabin relative to the chassis take place essentially linearly, i.e. that the degrees of movement freedom between the cabin and the chassis are restricted by virtue of the Watt linkage mechanism, in particular to vertical spring movements.
For example, such a suspension system is known from DE 10 2005 043 998 A1. Depending on the version concerned, this known suspension system comprises one or more Watt linkages, which ensure that the degree of movement freedom of the cabin relative to the chassis, for example in a truck, is restricted only to a vertical movement, or additionally that rolling movements of the cabin relative to the chassis are prevented. At the same time linear spring movements between the cabin and the chassis along the vertical axis—within the spring deflection range of the cabin—are still possible without restriction.
However, with this known suspension system it is still necessary, in the area of the Watt linkage arrangement, for separate and additional spring/damper elements to be disposed between the cabin and the chassis, since in accordance with the technical principle of the document the Watt linkage or linkages of the Watt linkage mechanism can only carry out guiding functions in relation to the vertical sprung movement, whereas the actual vertical holding forces or damping action during the sprung movement have to be provided by the separate spring/damper elements. Furthermore, for reasons of symmetry and design arrangement the spring/damper elements generally have to be provided in duplicate and are positioned in the area of two corners of the cabin.
This is elaborate and requires a comparatively large number of assemblies and components, which involve corresponding costs, corresponding structural space occupation and corresponding component weights. Besides, the spring/damper elements in the known driver's cabin suspensions are arranged in comparatively exposed positions and therefore have in their own right the need to be protected against damage or dirt during the often harsh day to day operating conditions of a truck.